Leftist and communist parties are a significant force in Indian politics.

In these elections they recorded their best ever performance, collectively winning 61 seats. The Communist Party of India (Marxist) is the third largest single party in the house with 43 seats.

The other principal parties on the left are the Communist Party of India (CPI), the All India Forward Bloc and the Revolutionary Socialist Party.

The left's key strongholds are the southern state of Kerala and the eastern state of West Bengal.

They also have a presence in Andhra Pradesh, Bihar, Tamil Nadu and Tripura.

Although the left's power base in West Bengal has eroded somewhat in recent times following a successful challenge posed by the BJP and its regional ally, the Trinamool Congress, they are still a formidable force in that state.

Their strength in Kerala and West Bengal is ascribed to their success in implanting land reform policies through which large farm holdings were broken up and distributed among the poor.

The CPI was the first communist party to formally join an Indian federal government, when they were part of the government of Prime Minister Deve Gowda in 1996.

A move to make veteran communist leader Jyoti Basu prime minister at the time came unstuck when his party, the CPI(M), rejected the move.

Although the communist parties have traditionally been opponents of Congress, they have identified the Hindu-nationalist BJP as their key political enemy and are therefor backing the Congress-led coalition government.